Lessons Learned from 7 BNR Upgrades
Authors:
- Paul Pitt, PH.D, P.E, Katya Bilyk, P.E., and Joe Rohrbacher, P.E. - Hazen and Sawyer
Many wastewater treatment plants in Virginia have just completed construction of biological nutrient removal (BNR) improvements. Their next challenge will be optimization and troubleshooting of the plants to produce the best effluent quality at the most economical cost. The purpose of this paper is to present seven practical lessons that have served other BNR facilities well in balancing effective treatment and cost.
(1) Plant A reduced its alum and carbon costs by $800,000 per year by optimizing its process configuration for nitrogen and phosphorus removal by optimizing the available carbon in the influent wastewater.
(2) Plant B piloting a new technology (IFAS) to determine its true operations and maintenance cost, which greatly improved the accuracy of their alternatives analysis, with significant lessons on plant operational issues.
(3) Plant C used sidestream treatment to cost effectively remove nutrients and enhance the reliability of its biological phosphorus removal (BPR) system. They also observed that receipt of alum sludge from a water treatment plant improved phosphorus removal and their nitrification safety factor, but had a negative effect on denitrification. Optimization of the online primaries has led to improved BNR performance.
(4) Plant D began feeding supplemental carbon to its 5-stage BNR plant, with improved BPR, and optimization of its primary anoxic zone to make the most of the readily biodegradable carbon in this zone.
(5) Plant E optimized its solids processing operations to ferment stored solids, returning a VFA-rich sidestream to the BNR process, which resulted in improved BPR and lower TN and TP loads from the plant.
(6) Plant F saved 10 million in capital cost by rerating and achieving nutrient removal with an innovative process configuration to maximize/optimize the existing infrastructure.
(7) Plant G utilized computational fluid dynamic modeling to optimize performance and increase the capacity of their secondary clarifiers.
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